Sub-50-nm self-assembled nanotextures for enhanced broadband antireflection in silicon solar cells

TLDR

Broadband antireflection materials are used for transparent windows, military camouflage, and efficient light coupling in solar cells and LEDs. The study investigates whether densely packed silicon nanotextures smaller than 50 nm can improve broadband antireflection beyond geometric predictions. The authors use block‑copolymer self‑assembly to create sub‑50‑nm silicon nanotextures, exploiting a surface layer with altered refractive index to enhance antireflection. The nanotexture’s reflectivity matches a model that includes surface refractive‑index changes, and its implementation on crystalline silicon cells yields a larger performance gain than an optimized planar antireflection coating. Rahman et al.

Abstract

Materials providing broadband light antireflection have applications as highly transparent window coatings, military camouflage, and coatings for efficiently coupling light into solar cells and out of light-emitting diodes. In this work, densely packed silicon nanotextures with feature sizes smaller than 50 nm enhance the broadband antireflection compared with that predicted by their geometry alone. A significant fraction of the nanotexture volume comprises a surface layer whose optical properties differ substantially from those of the bulk, providing the key to improved performance. The nanotexture reflectivity is quantitatively well-modelled after accounting for both its profile and changes in refractive index at the surface. We employ block copolymer self-assembly for precise and tunable nanotexture design in the range of ~10–70 nm across macroscopic solar cell areas. Implementing this efficient antireflection approach in crystalline silicon solar cells significantly betters the performance gain compared with an optimized, planar antireflection coating. Broadband light antireflection materials have numerous applications as highly transparent window, for broadband applications thin-film multilayers have been considered. Here, Rahman et al. demonstrate broadband antireflection enhancement in silicon solar cells using a self-assembled, nanostructured copolymer.